Thermionic tube circuits



Filed tJuly 50,`1942 2 Sheets-Sheet 2 PUSH-PULL ou'rPu'r Summon Cttorneg n Patented Dec. 14, 1948 THERMIONIC TUBE CIRCUITS Richard L. Snyder, Jr., Glassboro, N. J., assgnor to Radio Corporation of America, a corporation of Delaware Application July 30, 1942, Serial No. 452,820

14 Claims. (Cl. Z50-36) This invention relates generally to thermionic tube circuits and particularly to a' circuit utilizing a. thermionic tube which includes a plurality of control electrode elements. y

In thermionic vacuum tubes of the type including two control electrodes, a screen electrode and a suppressor electrode in addition to the usual cathode and anode electrodes, the first Vcontrol electrode may be connected to control directly the cathode current. The second ycontrol electrode may be arranged 'to control a-virtual cathode formed by the cathode emission, by maintaining the secondcontrol electrode ata slightly positive potential with respect to ground, a condition which may be established by connecting the cathode to ground through a cathode resistor. With such an arrangement, as therst grid is driven positive, the cathode will follow it,`and the second grid will become negative with respect to the cathode to reduce orcut ofi the anode current. Under these conditions the anode voltage changes in phase with the potentials applied to the rst control electrode. Various circuit arrangements, to be described hereinafter; may be employed to utilize the above described characteristics of such a thermionic tube for generating oscillations. By proper selection of feedback elements connecting the anode to the rst control electrode, or the screen to the second control electrode, or both, oscillations of complex vwave form may be generated under extremely stable operating conditions. The basic circuit may also be utilized to provide an amplier'in which the input and output potentials are substantiallyin phase. It should be understood Athat amplifiers according to the invention may be 'connected in cascade arrangement in the same'manner as 'conventional amplifiers. l

Among the objects of the invention are to provide a new and improved methodofl and means for generating oscillations by means of including a thermionic tube having a plurality'of control electrodes. Another object of the invention is to provide a new and improved method of and means for generating oscillations of complex wave form. Another object of the invention is to provide a new and improved method of and means for generating oscillations which utilizes a thermionic tube having a plurality of controlv electrode elements, in which the anode may be reactively coupled to the rst control electrode,- and the screen electrode may be reactively coupledto the second control electrode. Another object is to provide an improved method of and means for generating oscillations which utilizes a multithrough a cathode resistor element thermionic tube in which feedback is provided by a reactive circuit connected between the screen electrode and the second control electrode. Still another object of the invention is yto' provide a new and improved method of: and

means for generating oscillations which utilizes a multi-element thermionic tube in which the second control electrode is maintained at a potential positive with respect to the bias potential applied to the first control electrode.

Among other obects of the invention are to provide a new and improved method of and-means for amplifying signals wherein the output voltages are maintained in substantially the same phase as the input signals. Another Objectis to provide a new and improved method of and means 'for utilizing a single thermionic tube, havingv a plurality of control electrode elements, as lan amplier in which input potentials applied to one control electrode are amplified to derive inphase potentials in the anode circuit. Another object is to provide an improved method of and means for utilizing a multielectrode thermionic tube in which potentials applied to one'control electrode are amplified to derive in-phase voltages of increased amplitude in the screen electrode circuit. f I

The invention will be described by reference to the accompanying drawing of which Fig'. l'is a schematic circuit diagram of one'embodime'nt of said oscillator; Fig. 2 is a schematic circuit diagram of a second embodiment of saidvoscillator; Fig. 3 is a schematic circuit Adiagram of a third embodiment of said oscillator; Fig.; 4 is a schematic circuit diagram of one embodiment 'of said amplifier; and Fig. 5 is a schematic circuit diagram of a second embodiment of said amplier. Similar reference numerals are applied'to similar elements throughout the drawing.

Referring to Fig, l, a multi-element thermionic vacuum tube I, such as the RCA type 6L? is provided with heater and anode potentials, not shown. The cathode is connected to ground, and to the negative terminal of the anode power supply, 2.` The suppressor electrode R is connected to the cathode.` The positive terminal of the anode power supply is applied directly to the screen electrode S and through an anode resistor 3 to the-anode. The rst control electrode T is connected through a grid resistor 4 to ground. The second control electrode U is'connected to the positive terminal of a source of bias potential 5, which mayber a battery. The negative terminal of the source" of hie Potential 5 kis connected to ground, A' feedsith Output hilly be provided to a load through a i anode, and through a screen coupling ref Vsisten- IM3, to the screen electrode S. The negative trminai o f the anode power supply is connected to ground. The suppressor electrode R is connected to the cathode. The cathode is connected to ground through a cathode resistor 2.` The first control electrode T is connected to ground. The second control electrode U is also connected to ground through a grid resistor I4. yThe screen electrodeeis'i'connectedto the second control elec- .trodejhfrough a vfeedback circuit, Which includes n ca citdr I6. The feedback circuit may have inductive or capacitive characteristics.

blockingicapacitor connected to the tube anode lin Athesfanine manner as described and shown in the .circuit of Fig. 1.

In Fig. 3 a multi-element thermionic tube I,

.of the same type as described heretofore, includes sources of heater and anode potential, not shown. The positive terminal of the anode power source is connected to the anode through an anode resistor 3, and to the screen electrode S through the' screen resistor I3. The negative terminal ofthe anode power supply is connected to ground. The suppressor electrode R is connected to the cathode. The-cathodeis connected to ground through the cathode resistor 2. The first control jelectrode-T is connected `to ground through the `'igridg'resistor 4. The second control electrode U is .connected through the resistor I4 to the positive terminal of a source of bias potential 5, which may begabattery. 'The negative terminal of the sourcexpqtbiaspotential is grounded. ITwo feedircuitsare provided, which may be of Simi- ;.ditl'erentcharacteristics. The -iirst feed- ,j ticle-circuit which mondes a. switch il, a cstor-, and an inductor E is connected between .fthe anode and the rst-control electrode. By

operation of the switch -I I, the feedback circuit may Ibe -of eitherinductive or capacitive characteristics. The second feedback circuit, which includes a. switch I2, a capacitor I6, and an inductor IB is connected between the screen electrede and the `second control electrode. By opi eration of the switch I2, this feedback circuit may `also be of either inductive or capacitive characteristics. Blocking capacitors 8 and 8 respectively permit separate loads to be D.C. isolatedfrom the anode and screen asin the circuits of Figs.` land 2. The blocking vcapacitors also prevent shortcircuiting of the anode `and screen voltages through the inductors 6' and rIl'i whentheswitches II and I'2-are actuated.

Asexplained heretofore, when the second conl -f-,trolelectrode is maintained at apotential slightly g. positive with respect to ground, and the cathode it` connected to ground andto the negative termina] of.l the B-.powersupply through a cathode resistor, the cathode potential Will follow vthe first control electrodenpotential when that electrode is driven positive. The second control electrode will control the .anode .current from the virtual cathode, and will reduce or cut off the anode current in phase with the potentials on the lrst control electrode. With any of the feedback circuits described, the system will oscillate when suflicient reaction is provided. The apparent gain of the system may also be controlled by the feedback circuit connected between the screen electrode and the second/controlV electrode. As the second control-electrode is driven to a negative potential, the screen current will increase (due to the current cut off from the anode), and therefore, .the screen voltage will uctuate in phase with the voltage on the second control electrode, whereby the feedback circuit will provide continuous oscillations. As shown in Fig. 3, a combination of anode-to-rst control electrode, and screen-to-second control electrode feedback circuits may be utilized to provide oscillations of desired wave form and amplitude. Signals of different wave form may be derived simultaneously from the anode and screen electrode circuits. Signal characteristics may be determined by the feedback circuit and tube electrode circuit constants.

In Fig. 4 a multi-element thermionic vacuum tube I, such as the RCA type 6L?, is provided with heater and anode potentials, not shown. The cathode is connected to ground, and to the negative terminal of the anode power supply, through a cathode resistor 2 The suppressor electrode R is connected to the cathode. The positive terminal of the anode power supply is applied directly to the screen electrode S, and through an anode resistor 3 to the anode. The rst control electrode T is connected through a grid resistor 4 to ground. The second control electrode U` is connected through the switch arm 'I and the switch Contact A directly to ground. Input signals are applied betweenthe rst control electrode and ground. Amplied output signals are derived in any suitablemanner from between the anode and ground. When the switch arm 'I is connected to the switch contact B, the second control grid is connected to ground through a relatively Ahigh resistance I0, and is also connected to the anode through a suitable impedance such as a capacitor S-to provide desired degeneration. A

In Fig. `5, a multi-element thermionic tube I, of the same type as described in Fig. 1,.is provided with suitable sources of heater and anode p0- tentialS., not shown. The positive terminal of the anode power source is connected through the switch I 'I `directly to the anode, and through 'a `nals are obtainable by S. The negativeterminal of the anode power supply is connected to ground.A The suppressor electrode Ris connected to the cathode. The cathode is connected to ground through a cathode resistor 2. The rst control electrode T isr connected to ground. yThe second control electrode U is connected to ground through ashunt resistor 1 Input signals are applied to the tube between the second control'electrode and ground. The output signals `may be derived between the screen electrode and ground. It will be seen that the ampliiler circuits described are somewhat similar-to the oscillator circuits described heretofore with the exception that the feedback circuits have been omitted. Push-.pull output may also 'be derived -fronrthe circuit by connecting an an'- ode coupling resistor in parallel with the switch I'i. AWith theswitch open, push-pull output'fsigconnections 'betweenV4 the anode and the screen electrode. i

When the second Vcontrol electrode i'smainfftlned'at 'a potential slightly positive with respect I"to" ground, and the cathode is connected to ground through Va cathode resistor, the cathode potential Will/:follow the rst control .electrode potential when that electrode is driven positive. The second control electrode will control the anode current from the virtual cathode, and will reduce or cut oif the anode -current in phase with the po- ,tentia'ls on. the vrst vcontrol electrode. As the second-control electrode is driven to a negative -potential', the screen current will increase (due to Jthe current `cut-oil? from the anode), and Atherefre'gthe screen voltage will fluctuate in phase with he*voltage on the second control electrode.

'sJ-f-Thus-the invention comprises a new and im-` rproved'inethod of and means for utilizinga multi- VV-.elementl thermionic tube for generating oscilla- --tion'szofcomplex wave form. The oscillator described utilizes the in-phase characteristics of the'- anode and nrst control electrode, and the similarly in-phase characteristics of the screen electrode and second control electrode.

"The-invention also comprises a new and improved method of and means for utilizing a multielement thermionic tube for amplifying signals to derive Aoutput currents which are in phase with -`tlie'input vcurrents applied to the device. The :amplifier described utilizes the `in-phase charlacteristics of the first control electrode and the ).-lpdecircuits, or the similarly in-phase characteristics of the second control electrode and creen-electrode circuits.

*jl claim as my invention:

'1r- *1. l thermionic tube circuit including a tube having atleast a cathode, an anode, a screen le'ctrode and a plurality of control electrodes, vin'eans including a series cathode resistor connectfing said-cathode as a follower of one of said con- '.trol electrodes, means connected to said tube for `prf)vindingvoltages on said screen electrodel which are substantially in phase with voltages on one of said control-electrodes, means connected to said tube-for providing voltages on said anode which are substantially in phase' With voltages on another of said control electrodes, at least one feedr hack circuit connected to one of said control electrodes, and means for applying at least one of -fsaid voltages to said feedback circuit to control reaction 'within said tube circuit.

2. An oscillator including a thermionic tube I having a lcathode, an anode, a screen electrode, and a plurality of control electrodes, a source of anode potential positive with respect to said cathode, means connecting said positive anode potential to said anode and said screen, a source of bias potential positive with respect to said cathode, a cathode resistor, means including said resistor connecting said cathode to a point of reference potential, means connecting the first of said control electrodes to said point of reference potential, means for applying said positive bias potential to a second one of said control electrodes, reactive feedback means, and means connecting said feedback means between at least one of said control electrodes and at least one of said electrodes connected to said positive anode potential means.

3. An oscillator including a thermionic tube having a cathode, an anode, a screen electrode, and a plurality of control electrodes, a source of anode potential positive with respect to said cathode, means for applying said positive anode potential to said anode and said screen, a source of bias potential positive with respect to said cathode. a cathode resistor, means including lsaid resistor connecting said cathode to' a point of reference potential, means Vconnecting the first of said control electrodes to said point of reference potential, means for applying said positive bias potential to a second one of said control electrodes, capacitive feedback means, and means connecting said feedback means between at least one of said control electrodes and at least one of said electrodes connected to said positive anode potential means.

4. An oscillator including a thermio-nic tube having a cathode, an anode, a screen electrode, and a plurality of control electrodes, a source of anode potential positive with respect to said cathode, means for applying said positive anode p0- tential to said anode and said screen, a source of bias potential positive vwith respect to said cathode, a cathode. resistor, means including said erence potential, means connecting the first of vsaid control electrodes to said point of reference potential, means for applying said positive bias potential to a second one of said control electrodes, inductive feedback means, and means connecting said feedback means between at least one of said control electrodes and at least one of said electrodes connected to said positive anode potential means.

5. An oscillator including a thermionic tube having a cathode, an anode, a screen electrode, and a plurality of ycontrol electrodes, a source of anode potential positive with respect to said cathode, means for applying said positive anode potential to said anode and said screen, a source of bias potential positive with respect to said cathode, a cathode resistor, means including said resistor connecting said cathode to a point of reference potential, means connecting the rst of said control electrodes to said point of reference potential, means for applying said positive bias potential to a second one of said control electrodes, reactive feedback means, and means connecting said feedback means between said first control electrode and said anode.

6. An oscillator including a thermionic tube having a cathode, an anode, a screen electrode, and a plurality of control electrodes, a source of anode potential positive with respect to said cathode, means for applying said positive anode potential to said anode and said screen, a source of bias potential positive with respect to said cathode, a cathode resistor, means including said resistor connecting said cathode to a point of reference potential, means connecting the first of said control electrodes to said point of reference potential, means for applying said positive bias potential to a second one of said control electrodes, reactive feedback means, and means connecting said feedback means between said second control electrode and said screen electrode.

7. An oscillator including a thermionic tube having a cathode, an anode, a screen electrode, and a plurality of control electrodes, a source of anode potential positive with respect to said cathode, means for applying said positive anode potential to said anode and said screen, a source of bias potential positive with respect to said cathode, a cathode resistor, means including said resistor connecting said cathode to a point of reference potential, means connecting the first of said control electrodes to said point of reference potential, means for applying said positive bias potential to a second one of said control electrodes, rst reactive feedback means, means connecting said feedback means between said rst control electrode and said anode, second reactive feedback means, and means connecting said second feedback means between said second control electrode and said screen electrode.

8. A device of the type describedy in claim 5 including a load circuit, and means for connecting said load circuit to said device.

9. A device of the type described in claim 6 including a load circuit, and means for connecting said load circuit to said device.

10. A device of the type described in claim 7 including a load circuit, and means for connecting said load circuit to said device.

11. An amplifier for deriving amplied output signals of substantially the vsame phase as signals applied to the input of said amplifier including a thermionic tube having a, cathode, an anode electrode, a screen electrode and a plurality of control electrodes, means including a `series cathode resistor for biasing onel of said control electrodes to a potential which is negative with respect to said cathode, a source of anode voltage positive with respect to said cathode, means for applying said positive anode voltage to said anode electrode and said screen electrode, means for applying said input signals between another of said control electrodes and said cathode, means coupling said anode to said one of said control electrodes for providing degeneration, and means for deriving amplied signals of substantially the same phase as said input signals from one of said electrodes connected to said positive voltage source.

12. An amplier for deriving ampliiied output signals of substantially the same phase as signals applied to the input of said amplifier including a thermionic tube having a cathode, an anode, a screen electrode and a plurality of control electrodes, means including a series cathode resistor for biasing the second of said control electrodes to a potential which is negative with respect to said cathode, means for applying said input signals to the first of said control electrodes, degenerative feedback means, means connecting said feedback means between said anode and said second control electrode, and means for deriving signals of substantially the same phase as said input signals from between said anode and said cathode.

13. In a signal amplifier including a thermionic tube having a cathode, an anode, a screen electrode and a plurality of control electrodes, the method comprising actuating said cathode as a. follower of one of said control electrodes, applying signals to another of said control electrodes, providing degeneration between said anode and one of said control electrodes, and deriving from said amplier amplied signals of substantially the same phase as said applied signals.

14. In a signal amplifier including a thermionic tube having a cathode, an anode, a screen electrode and a plurality lof control electrodes, the method comprising actuating said cathode as a follower of one of said control electrodes, applying signals to another of said control electrodes, providing degeneration between said .anode and one of said control electrodes, and deriving rfrom said anode and said cathode amplified signals of substantially the same phase as said applied signals.

RICHARD L SNYDER, Jn.

REFERENCES CITED The following references are of record in the `die of this patent:

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